Instrument for mixing dental materials and the like



Aug. 15, 1967 R. F'. SPINELLO INSTRUMENT FOR MIXING DENTAL MATERIALS ANDTHE LIKE Filed Aug. 20, 1965 INVENTOR. 7??!20 Ronald P 5,222

,4 Trap/V1575.

United States Patent 3,336,009 INSTRUMENT FOR MIXING DENTAL MATERIALSAND THE LIKE Ronald P. Spinello, Westbury, N.Y., assignor to TheDentists Supply Company of New York, York, Pa., a

corporation of New York Filed Aug. 20, 1965, Ser. No. 481,263 8 Claims.(Cl. 259-8) ABSTRACT OF TI-E DISCLOSURE A mixing device for trituratingdental materials such as amalgams and in which a yieldable helicalspring rotates in a chamber to cause continuous mixing movement of theingredients and also discharge the same by such rotating spring torender the device substantially selfcleaning.

Mixing small quantities of materials having high densities or shearcharacteristics such, for example, as dental amalgams, is difiicult.Historically, and to -a large extent today, it is done manually with amortice and pestile. The operation is not ony time-consuming but it isrelatively critical because, in the case of amalgams, the particles ofsilver and the liquid mercury must be brought into intimate contact in auniform mixture as part of the process called trituration. The materialhas only a transient phase in which it is suitably pliant to becondensed in a tooth cavity to form an effective filling. On the otherhand if it is not thoroughly triturated, a low quality filling alsoresults even though hardening has not set in prior to the condensingoperation.

The combination of relatively long periods for manual mixing andpossible low-quality results have given rise to various attempts tomechanize the operation.

The character of the material and the small amounts which are normallymixed at one time has not yielded to an effective, economical solution.A typical mechanical aid evolves the use of a small container or capsuleinto which the materials are placed and thereafter agitated untiltrituration occurs. The difiiculty of loading of the capsules, the noiseand time of the agitation, and the difiiculty of removing the amalgamfrom the capsules represent some of the objections to this approach tomechanization.

Accordingly, it is an object of the present invention to provide animproved mixing instrument particularly adapted for triturating metalparticles and mercury.

A further object of the invention is to provide an instrument fortriturating dental amalgam which greatly simplifies the loading andunloading process and which is self-cleaning.

Still another object of the invention is to provide an improved mixinginstrument which is capable of accommodating extremely small quantitiesof material and which is capable of carrying out mixing processes suchas trituration in minimum time with minimum attendant noise.

In accordance with the present invention, metered quantities of basicmaterials are deposited in a mixing chamber, preferably in the form of asmall, vertically disposed cylindrical cavity. A mixing rotor isdisposed in the cavity in the form of a helically wound wire elementcoupled to a drive motor for rotary motion. The drive is preferablyarranged so that the rotor is driven in a predetermined direction inrelation to the pitch of the helix, viz so that the material engaged bythe helix is driven downward. The helical rotor is preferably underslight axial compression within the chamber against a base, which cantake the form of a valve plate movable to release the completed mixture.

3,336,009 Patented Aug. 15, 1967 In operation, assuming a dental amalgamis being triturated, metallic particles and mercury are deposited in thechamber and the rotor is driven to cause the mixture to be mulled withinthe chamber until trituration occurs. The mixture at the walls of thechamber is driven downward toward the base and the material in thecenter is squeezed upward until it is again caught in the downward flow.The rapid flow and attendant reversals of direction result in intimatecoaction of the materials. When the load on the rotor is heavy, thehelical rotor is automatically compressed upwardly to lighten the loadand maintain good mixing speed. Upon completion of the mixing cycle, avalve is then opened and the amalgam is released from the instrument,preferably under the combined effects of gravity and the thrust of therotating helical rotor, which also scavenges the walls of the chamber ofall residue material. After the material is discharged the valve isclosed, first compressing the extended helical rotor which, in onepreferred arrangement of the invention can be made to drive itselfbackward into the chamber to its previous compression state to rest onthe base or valve plate under compression awaiting the next load.

Other objects and features of the present invention will be apparentfrom the following description of one preferred embodiment thereof takenin conjunction with the accompanying drawings in which:

FIGURE 1 is a view in side elevation and partly broken away in verticalsection of a mixing instrument particularly adapted for amalgamtrituration;

FIGURE 1A is a fragmentary view in vertical section of a portion of theinstrument of FIGURE 1; and

FIGURE 2 is a view in horizontal section taken on the line 22 of FIGURE1, looking in the direction of the arrows and showing the design andoperation of the base valve.

Referring to the drawing, the invention is illustrated as embodied in amixing instrument 10*, particularly designed for the trituration ofamalgams in a dental office. The instrument 10 includes a supportingframe 11 having a base 12 adapted to rest on a table, for example, and avertical support 13 carried thereby. A mixing chamber 14, preferablytaking the form of a housing having a vertically arranged cylindricalmixing cavity 14a is supported by the frame by means of a fixed bracketarm 15 secured to the vertical member 13.

An electrical drive motor 16 is also fixed to the support member 13 by amounting bracket 17 with its output drive shaft 16a disposed above themixing chamber 14a in coaxial alignment therewith. The motor 16 isadapted to be energized from a suitable electrical source 18 through anelectrical switch control 18', both schematically illustrated in thedrawing for purposes of simplicity. Secured to the rotor or drive shaft16a to turn therewith is a rotary mixing element 19 in the form of ahelically wound spring element. The lower end of the helical mixingelement 19 bears against a valve plate 20, which normally covers thelower end of the mixing chamber 14a. The plate valve 20 is mounted forpivotal movement on a vertical shaft 21 carried by the bracket arm 15 sothat it can be swung horizontally by means of its forwardly extendinghandle 20a. The valve plate 20 includes a circular opening 20b ofapproximately the same diameter as the mixing chamber 14a and, disposedto one side thereof, a bearing surface 200. In its closed position thebearing surface 200 is disposed beneath the mixing element 19 and coversthe bottom opening of the vertical chamber 14a. In its open position thevalve plate is swung to dispose the discharge opening 20b beneath thechamber 14a, allowing the contents thereof to be discharged as will bemore fully described below. A limit stop pin 22 working in an arcuateslot 20d that disclosed in the applicants copending application, 7

Ser. No. 437,806 filed Mar. 8, 1965, and now abandoned and entitled,Amalgam Conveyor and Method of Condensing Amalgam.

Materials to be mixed or triturated such, for example, as mercury andsilver particles, are introduced into the mixing chamber 141: through aninlet chute 25. In the case of an amalgam triturating instrument, theinput can take the form of a metering dispenser capable of accommodatingliquid mercury and metal particles either in loose form or in compressedpellet form.

In operation, it will be assumed that metered charges of mercury andsilver particles or filings have been introduced into the chamber 14athrough the inlet chute 25 falling under the force of gravity to thebottom of the chamber resting -on the bearing plate 20c of the valveplate 20 and filling the chamber to a point below the inlet chute 25.The motor 16 having previously been turned on by means of a switch 18,causes the helical rotor member 19 to be rotated at relatively highspeed in a counterclockwise direction as viewed downwardly from the topof the chamber 14a. This motion assists in the movement of raw materialsto the bottom of the chamber as well as carrying out the mixing cycledescribed below. It will be observed that the pitch of the helicalmember 19 is positive so that as it is turned in a clockwise direction,as viewed from the top, it will tend to drive material within itsinfluence downwardly. Stated otherwise, the pitch is such that were itdisposed in a solid medium, it would tend to back out of the medium inthe manner of a screw.

The initial reaction of the member 19 against the mass of material to bemixed will therefore tend to compress the spring upwardly against itsnatural spring force and the combined agitation of the whirling springdriving downwardly under its spring force will mull or triturate thematerials Within the chamber. The action is such that materialsproximate the walls of the chamber will be driven downward to be urgedtoward the center and squeezed upwardly from the base plate, and thenceradially outwardly into the down flow in a rapid succession of reversalsof direction and intimate commingling of the components of the mixresults.

In one preferred unit formed in accordance with the inventionparticularly adapted for effecting trituration of a useful quantity ofdental amalgam composed of silver particles and mercury, a cylindricalmixing chamber of .250 inch was used with a helical rotor or springhaving an outside diameter of .218 inch wound at a pitch of ten turnsper inch using stainless steel wire of .032 inch diameter. A nominaldrive speed of 3600 r.p.m. was used and the helical spring wascompressed approximately eight percent by the base or valve plate 20. Itshould be noted that the helical member operates in a close proximity tothe walls of the chamber, and that in motion it sweeps or eclipses theentire surface area of the chamber while maintaining an open centralcore.

The time to complete the trituration of one charge of amalgam was aboutfive seconds. During this time the helical spring element initiallybacked off the base of the valve plate and re-es-tablished contact atthe conclusion of the mixing cycle. The slight change in tone of the lowlevel sound emitted from the unit as the element made contact with thebase 20 was an eilective indicator of completion of the cycle.

At the completion of the mixing cycle, but before the drive motor 16 isde-energized the valve plate 20 is swung into its open position i.e.with the opening 20b disposed beneath the chamber 14a and the amalgam isdischarged by the conveyor action of the rotating spring element intowhatever receptacle or instrument might be disposed in receivingposition. The rotation of the element coupled with gravity scavengesloose material from the walls of the unit. It will be understood,therefore, that the helical rotor or spring element serves as a conveyorboth at the time of top loading (it used) and at the time of discharge.

The plate valve is then swung to its closed position with the edge ofthe hole 20b in the valve plate engaging the lower coils of the rotatinghelical element causing it by virtue of its pitch in relation to thedirection of rotation, to back up into the mixing chamber 14a and reston top of the valve plate 20 above the bearing surface 201: ready forthe next charge.

While a relatively wide range of pitch angles and spring constants canbe used for the helical mixing element 19, it is in general preferredthat the spring force be such that the member is able, while rotating inthe mass of material being mixed, to work its way down to the valveplate when mixing is completed so that there are no pockets or cavitiesbetween the fixed walls of the chamber and the rotor which are reached.It will be understood, however, that under certain conditions the rotorspring need not back oil the valve plate during the mixing operation.The ability, however, of the rotor to compress in action serves as anautomatic means for relieving extraordinary stresses on the system andfor maintaining effective mixing speeds at all times.

It will also be understood that the mixing apparatus can take variousother forms and arrangements within the scope of the present invention.Thus, for example, the laterally swinging valve plate 20 can be replacedby a vertically movable plug element adapted to be inserted into thedischarge nozze 23, compressing the spring rotor 19 as desired. Sucharrangement has the advantage of affording variable compression on thespring rotor 19 for use in mixing other materials which might requiregreater or less downward pressure. It is also possible to load thematerials to be mixed through the bottom rather than through the inletchute 25 or other top loading means. In the case of bottom loading it isnot necessary that the motor be energized at the time of introducing thecharge into the mixing chamber as is preferred in the case of an upperinlet such as the chute 25 where the action on the helical rotor assistsin thrusting the charge, particularly granular matter, to the bottom ofthe chamher to set up conditions for thorough mixing. Automatic timingcan be used for particularly critical operations which can becoordinated with other operations. Other variations and arrangementswill suggest themselves to those skilled in the art. The inventionshould not, therefore, be regarded as limited except as defined in thefollowing claims.

I claim:

1. Apparatus for mixing dental amalgam comprising a substantiallycylindrical chamber having inlet means to receive amalgam ingredients tobe mixed and said chamber having a discharge opening adjacent one endthereof, closure means normally extending across said opening to closeit, a helical resilient member substantially complementary to the innersurface of said chamber and rotatable therein about the axis thereof,the interior of said helical member defining a substantially cylindricalcentral opening extending axially thereof and said member also extendingbetween said inlet means and said closure means, and power meansconnected to said helical member to rotate it as aforesaid to effectmulling of amalgam ingredients within said chamber.

2. Apparatus for mixing dental amalgam comprising a substantiallycylindrical chamber having inlet means to receive amalgam ingredients tobe mixed and one end of said chamber comprising a discharge opening,closure means normally extending across said opening to close it, ahelical resilient spring substantially complementary to the innersurface of said chamber and rotatable therein about the axis thereof,said spring extending between said inlet means and said closure meansand being sufiiciently long to be compressed axially a limited amountwhen one end thereof is in engagement with said closure and said one endslidably moving relative to said closure when said spring is rotated,thereby efl'ectively engaging material in contact with said closuremeans, and power means connected to said helical member to rotate it asaforesaid to effect mulling of amalgam ingredients within said chamber.

3. Apparatus for mixing dental amalgam comprising a substantiallycylindrical chamber having inlet means to receive amalgam ingredients tobe mixed and one end of said chamber comprising a discharge opening, aclosure member movable substantially transversely in opposite directionsrelative to the axis of said chamber to open and close said dischargeopening, a helical resilient member substantially complementary to theinner surface of said chamber and rotatable therein, said resilientmember also extending between said inlet and outlet means and beingsufficiently long to project into said discharge opening when saidclosure has been moved to open position, thereby to induce self-cleaningof said discharge opening when mixed amalgam is discharged therethrough,and power means connected to said helical member to rotate it asaforesaid to effect mulling of amalgam ingredients within said chamber.

4. The apparatus according to claim 3 in which said closure is ofsufficient area to include a hole complementary in size to the diameterof said chamber and registerable therewith when said closure ispositioned to open said discharge opening and said closure alsoincluding a solid portion equal to the diameter of said chamber andpositionable across the same to maintain said discharge opening closed.

5. The apparatus according to claim 4 further including a pivot for saidclosure parallel to the axis thereof and spaced laterally therefrom, andhandle means on said closure extending outwardly from said chamber andoperable manually to move said closure between open and closedpositions.

6. The apparatus according to claim 3 in which said power means isarranged to rotate said resilient helical member in a direction relativeto its pitch so that when said plate-like closure is moved from open toclosed position, said resilient member will engage an edge on saidclosure and effect compression of said resilient member from theextended position thereof sufliciently to engage the inner surface ofsaid closure and enable it to move laterally past the resilient memberto fully closed position.

7. Apparatus for mixing dental amalgam comprising a substantiallycylindrical chamber having inlet means to receive amalgam ingredients tobe mixed and one end of said chamber comprising a discharge opening, aclosure member extending transversely across said chamber adjacent saiddischarge opening to form a bottom in said chamber and said inlet meansintersecting a wall of said chamber intermediately of the ends thereof,a helical resilient member substantially complementary to the innersurface of said chamber and rotatable therein about the axis thereof,said helical member extending at least between said inlet means andclosure means and intersecting the incoming amalgam ingredients whenentering said chamber through said inlet means, and power meansconnected to said helical member to rotate it as aforesaid to effectmulling of amalgam ingredients within said chamber.

8. The apparatus according to claim 7 in which said helical member is aspring closely conforming to the interior of said chamber and at leastlightly engaging the walls thereof and said power means being connectedto the upper end of said spring and arranged to rotate it in a directionrelative to its pitch to engage and force the amalgam material towardsaid discharge opening, the central core space'of said spring comprisingmeans in which amalgam material may pass in the opposite direction tothat by which it is moved by said spring, thereby effecting efficientmulling of said amalgam.

References Cited UNITED STATES PATENTS 882,781 6/ 1906- Smith. 1,249,40312/1917 Howard et al. 2597 2,641,412 6/1953 Byberg 2598 X 2,791,4045/1957 Kelley et al. 2599 2,884,963 5/1959 Erndt 2598 X 3,063,81311/1962 Yeinbrenner et al. 2597 X 3,224,740 12/1965 Kuehn et al. 2598FOREIGN PATENTS 448,553 6/1936 Great Britain.

WILLIAM I. PRICE, Primary Examiner. WALTER A. SCHEEL, Examiner. J. M.BELL, Assistant Examiner.

1. APPARATUS FOR MIXING DENTAL AMALGAM COMPRISING A SUBSTANTIALLYCYLINDRICAL CHAMBER HAVING INLET MEANS TO RECEIVE AMALGAM INGREDIENTS TOBE MIXED AND SAID CHAMBER HAVING A DISCHARGE OPENING ADJACENT ONE ENDTHEREOF, CLOSURE MEANS NORMALLY EXTENDING ACROSS SAID OPENING TO CLOSEIT, A HELICAL RESILIENT MEMBER SUBSTANTIALLY COMPLEMENTARY TO THE INNERSURFACE OF SAID CHAMBER AND ROTATABLE THEREIN ABOUT THE AXIS THEREOF,THE INTERIOR OF SAID HELICAL MEMBER DEFINING A SUBSTANTIALLY CYLINDRICALCENTRAL OPENING EXTENDING AXIALLY THEREOF AND SAID MEMBER ALSO EXTENDINGBETWEEN SAID INLET MEANS AND SAID CLOSURE MEANS, AND POWER MEANSCONNECTED TO SAID HELICAL MEMBER TO ROTATE IT AS AFORESAID TO EFFECTMULLING OF AMALGAM INGREDIENTS WITHIN SAID CHAMBER.